Emergence of the precore mutant late in chronic hepatitis B infection correlates with the severity of liver injury and mutations in the core region

HBeAg-Negative/Anti-HBe-Positive Chronic Hepatitis B: A 40-Year-Old History

Hepatitis B “e” antigen (HBeAg) negative chronic hepatitis B (CHB), 40 years since discovery in the Mediterranean area, has become the most prevalent form of HBV-induced liver disease worldwide and a major health care burden caused by HBV infection. A great deal of knowledge accumulated over the last decades provides consistent evidence on the bimodal dynamics of the expression of structural and non-structural forms of the viral core proteins which associate with different virologic and clinic–pathologic outcomes of HBV infection. In absence of serum HBeAg, the presence and persistence of HBV replication causes and maintains virus-related liver injury. Thus, in clinical practice it is mandatory to screen HBV carriers with HBeAg-negative infection for the early diagnosis of HBeAg-negative CHB since antiviral therapy can cure HBV-induced liver disease when started at early stages.

Is the function of the HBeAg really unknown?

The immune response to the hepatitis B virus (HBV) vaccine in newborns of hepatitis B e antigen (HBeAg)-positive or HBeAg-negative mothers is the subject of Huang et al. The authors report no correlation between the HBeAg status of the mothers/cord blood and the newborns immune response to the vaccine, but, unfortunately, draw unfounded conclusions regarding the tolerogenic potential of in utero exposure to HBeAg. In this reply, I address the possible influence of in utero exposure to the HBeAg, and briefly review other characteristics of the HBeAg, that may promote HBV chronicity. I argue that the function of HBeAg should no longer be considered "unknown" and that immunotolerance/immunomodulation represent the dominant functions of the HBeAg in viral-host interactions.

HBeAg negative variants and their role in the natural history of chronic hepatitis B virus infection

Molecular virology methods including polymerase chain reaction, cloning and sequencing have revolutionised our understanding of viral genome variation. In the case of hepatitis B virus (HBV), sequencing studies have identified a number of virus variants normally found during the natural course of chronic infection. The appearance of the precore stop codon (with G-for-A substitution at position 1896) and basal core promoter (BCP) (with A-for-T and G-for-A, at positions 1762 and 1764, respectively) variants which reduce or abrogate hepatitis B e antigen (HBeAg) production, heralds the initiation of the seroconversion phase from HBeAg to anti-HBe positivity. The gradual removal of the tolerogenic effect of HBeAg leads to the awakening of the immune response (immune clearance phase). Most patients after HBeAg seroconversion become “inactive HBsAg carriers”. However during the course of infection precore and/or BCP variants may emerge and be selected leading to HBeAg negative chronic hepatitis B (CHB) with high viremia levels (reactivation phase). The prevalence of HBeAg negative CHB has been increasing over the last few decades and has become the commonest type of HBV infection in many countries of the world. This probably reflects the aging of existing HBV carriers and the effective prevention measures restricting new HBV infections. Frequent acute exacerbations accompanied by high viral replication, elevated alanine aminotransferase levels and histological activity are a common feature of HBeAg negative CHB leading to cirrhosis much faster than in HBeAg positive CHB patients.

Number of mutations within CTL-defined epitopes of the hepatitis B Virus (HBV) core region is associated with HBV disease progression

The virologic determinants of progressive liver disease associated with hepatitis B virus (HBV) remain unclear. Previous investigations have associated HBV disease with specific mutations but this association may be confounded by HBV genotype, HLA haplotype of the infected individual or both. The association between non-synonymous mutations located within putative cytotoxic T-lymphocyte directed epitopes (CDE) of the HBV core region and disease states was investigated. Subjects infected with HBV were enrolled from a clinical cohort in Seoul, Korea, and HBV core gene sequences were analyzed for mutational patterns inside and outside of CDE with respect to subject demographics and HBV-related disease states. No specific mutation or pattern of mutations were associated with progressive disease states; however, individuals with cirrhosis and hepatocellular carcinoma had greater numbers of non-synonymous mutations within CDE when compared to those with chronic HBV infection who were HBeAg positive (P = 0.007 and 0.026, respectively). In conclusion, this study demonstrates that HBV disease progression is associated with viral escape mutations that are a marker of CTL activity. These data suggest that the number of non-synonymous mutations in the HBV core region may predict HBV disease progression better than any single mutation or pattern of mutations.

An outbreak of hepatitis B with high mortality in India: association with precore, basal core promoter mutants and improperly sterilized syringes

In 2009, an outbreak of hepatitis B with high mortality was observed in Sabarkantha district, Gujarat state, India with 456 cases and 89 deaths. Hospitalized patients with self-limiting disease (152, AVH)) and fulminant hepatic failure (39, FHF including 27 fatal and 12 survivals) were investigated. These were screened for diagnostic markers for hepatitis viruses, hepatitis B virus (HBV) genotyping and mutant analysis. Complete HBV genomes from 22 FHF and 17 AVH cases were sequenced. Serosurveys were carried out in the most and least affected blocks for the prevalence of HBV and identification of mutants. History of injection from a physician was associated with FHF and AVH cases. Co-infection with other hepatitis viruses or higher HBV DNA load was not responsible for mortality. Four blocks contributed to 85.7% (391/456) of the cases and 95.5% (85/89) mortality while two adjacent blocks had negligible mortality. Sequence analysis showed the presence of pre-core and basal core promoter mutants and 4 amino acid substitutions exclusively among FHF cases. None of the self-limiting patients exhibited these dual mutations. Genotype D was predominant, D1 being present in all FHF cases while D2 was most prevalent in AVH cases. Probably due to violation of accepted infection control procedures by the qualified medical practitioners, HBV prevalence was higher in the affected blocks before the outbreak. Gross and continued use of HBV contaminated (mutant and wild viruses) injection devices led to an explosive outbreak with high mortality with a striking association with pre-C/BCP mutants and D1 genotype.

Characterization of the basal core promoter and precore regions in anti-HBe-positive inactive carriers of hepatitis B virus

BACKGROUND

The study of hepatitis B virus (HBV) genomic heterogeneity has become a major issue in investigations aimed at understanding the relationship between HBV mutants and the wide spectrum of clinical and pathological conditions associated with HBV infection. Although most chronically infected HBV patients are inactive carriers, several virological aspects of this state remain unclear.

METHODS

In order to determine the prevalence and clinical significance of mutations in the basal core promoter (BCP) and precore (pC) regions among inactive carriers, the nucleotide sequences from 41 inactive carriers were analyzed and compared with those from 29 individuals with chronic active hepatitis.

RESULTS

Genotypes A (24.3%), D (37.1%), F1b (12.9%), and F4 (18.6%) were the most prevalent. Mutations in the BCP/pC regions were observed in most of the inactive carriers (92.7%) and in most of the patients with chronic active hepatitis (93.1%). The prevalence of mutation 1764(A) was significantly higher in patients with chronic active hepatitis (65.5%) than in inactive carriers (36.6%) (p=0.038), whereas the prevalences of mutations at the other positions analyzed were not significantly different. Older patients (>50 years) showed BCP/pC patterns with a higher number of substitutions. Mutations were found to be biased by genotype: the 1896(A) mutation was highly prevalent in genotypes D and F4, while alternative substitutions in the pC region were more prevalent in genotypes A and F1b.

CONCLUSIONS

Mutations in the BCP/pC regions are the hallmark of chronic anti-HBe-positive individuals; nevertheless, the even distribution of mutations in active and inactive carriers suggests that BCP/pC mutations may occur during HBV infection not strictly related to the HBV infection activity.

Hepatitis B e-antigen persistency is associated with the properties of HBV-specific CD8 T cells in CHB patients

To investigate the correlation between the HBeAg and the properties of HBV-specific CD8 T cells, as well as liver injury, serum HBV markers, liver histology, the frequency and phenotypic characteristics of CD4(+)CD25(+) Treg and HBV-pentamer(+) CD8 T cells were measured. No significant differences between the median serum ALT levels, the frequency and Foxp3 expression of CD4(+)CD25(+) Treg, and liver fibrosis were observed. Higher HBV DNA levels in HBeAg(+) patients were observed, while liver necroinflammation was more severe in HBeAg(-) patients. Differences in HBV-pentamer(+) T cell frequency were not significant, but increased PD-1 and CTLA-4 expression on HBV-specific CD8 T cells was seen in the HBeAg(+) group. HBV-peptide stimulation with anti-PD-L1 and anti-CTLA-4 significantly increased the proliferation in PBMCs from both groups, but enhanced IFN-γ production only in the HBeAg(+) patients. Therefore, HBeAg persistency in CHB patients probably increased the expression of PD-1 and CTLA-4 on HBV-specific CD8 T cells, which may be associated with the low intensity of T cell responses and high HBV DNA load.

Subgenotypes of hepatitis B virus genotype D (D1, D2, D3 and D5) in India: differential pattern of mutations, liver injury and occult HBV infection

Hepatitis B genotype D (HBV/D) is the most widespread genotype and exists as at least five subgenotypes (HBV/D1-D5). However, little is known about the association of virological characteristics with clinical differences among HBV/D subgenotypes. To investigate the virological characteristics of these subgenotypes and their clinical implications, we selected a cohort of 109 genotype D infected individuals from the state of West Bengal, India, including 68 HBsAg positive patients and 41 with occult HBV infection. Among the HBsAg positive subjects 28 had chronic hepatitis B virus infection, 40 were asymptomatic carriers based on clinical examination, liver function test and ultrasonograph results. Overall, HBV/D1 was found in 17%, HBV/D2 in 29%, HBV/D3 in 34% and HBV/D5 in 20% of the cases. HBV/D1 was significantly associated with chronic liver disease (P = 0.01), and in this subgenotype A1896 (PreC mutations) were most common. Although BCP mutations (A/C1753 and T1762/A1764) were found to be frequently associated with HBV/D2 (33% and 33%) and D5 (47% and 59%), no apparent clinical correlation was observed. On the other hand, occult HBV infection was significantly associated with HBV/D3 infection, along with low level of BCP and PreC mutations and several non-synonymous substitutions in the catalytic reverse transcriptase (RT) domain of polymerase gene. Similar nucleotide substitutions in the surface (S) gene region were observed from both northern and eastern Indian HBV/D3 isolates. In conclusion, HBV/D subgenotypes differ in their mutational patterns in the S, polymerase and the BCP/PreC regions that may influence their clinical outcomes.

Core mutations in patients with acute episodes of chronic HBV infection are associated with the emergence of new immune recognition sites and the development of high IgM anti-HBc index values

Acute exacerbations in HBeAg negative patients with chronic hepatitis B virus (HBV) infection are invariably associated with concurrent increases in the index of IgM class antibodies against the core protein (anti-HBc) of the virus. This study aimed to investigate whether this was related to the clearance of variants from the quasispecies pool and the appearance of new ones, with aminoacid substitutions in well recognized B-cell epitopes. In this study, 5 HBeAg negative patients (A to E) with 13 sequential serum samples (A1-A2, B1-B2-B3, C1-C2, D1-D2-D3, E1-E2-E3) were investigated after amplification of the entire core encoding region followed by cloning/sequencing studies. The sequences at different time points were compared with those from a single HBeAg positive patient with no apparent acute exacerbations. The results from sequence comparison showed that virus variants emerged in all (A2, B3, C2, D3, E2, and E3) but two (B2 and D2) subsequent sera with amino-acid substitutions affecting B-cell epitopes. It is concluded that the rise in the values of IgM anti-HBc may be attributed to the alteration of the antigenic epitopes leading to new antibody production in the majority of the cases. However, it appears that increases in IgM anti-HBc indexes in a few cases may relate to other possible mechanisms which are discussed.

Validation and comparison of different PCR-based methods for detection of hepatitis B virus precore region mutants

Hepatitis virus variants detection is useful in clinical practice; however, methods that are used for their identification may influence the results significantly. Three PCR-based assays for quantitation of G1896A precore HBV mutants: two allele specific PCRs, single tube (single-AS-PCR) with enzymatic restriction or separate tubes (twin-AS-PCR) and one oligohybridization assay (OA) with three probes were developed and standardized. Wild type and mutant plasmids and 10 sera were used as reference. All methods had sensitivity limits of 10(4)copies/ml and their specificity encompassed 3 logs (10(4)-10(7)copies/ml) with dynamic ranges of logs for OA, twin-AS-PCR and single-AS-PCR, respectively. Single-AS-PCR and OA detected minor viral populations when their relative prevalence was at least 10% of the overall viral population whereas their detection by twin-AS-PCR ranged from 0.1 to 10% for samples with 10(7) and 10(5)copies/ml viral loads, respectively. Twin-AS-PCR was the most sensitive to detect the minor viral population, whereas single-AS-PCR and OA were more accurate to quantify the relative proportions of the two viral populations independently of the overall viral load. In conclusion, an accurate characterization of HBV precore heterogeneity should be warranted by a careful choice of the most appropriate assay according to the aim of the study.

Decreased frequency and function of circulating plasmocytoid dendritic cells (pDC) in hepatitis B virus infected humans

The Type 2 precursor plasmacytoid dendritic cells (pDC) represent the most important cell type in antiviral innate immunity. To understand the function of pDC during hepatitis B virus infection, the frequency and function of circulating pDC were analyzed by flow cytometric analysis, and IFN-alpha secretion of total PBMCs was determined by ELISA assay in 25 healthy subjects and 116 patients at various stages of chronic hepatitis B virus infection (CHB). The number of circulating pDC was found to be significantly lower in patients with CHB and associated liver cirrhosis (LC). The ability of PBMCs to secrete IFN-alpha also decreased significantly. There was a corresponding decrease of circulating NK cells and CD8+ T cells. We observed that lamuvidine antiviral therapy restored the number of circulating pDC and there was a reversal of pDC frequency with the control of HBV replication in chronic HBV patients, indicating these subjects are unlikely to be totally immunocompromised. The decrease of pDC was found to be related to nosocomial infections in LC patients. Our results suggest that CHB patients probably have a quantitative and qualitative impairment of circulating pDC or NK cells, which may be associated with HBV persistent infection as well as the nosocomial infections that arise in LC patients.

Comparative study of genotype B and C hepatitis B virus-induced chronic hepatitis in relation to the basic core promoter and precore mutations

BACKGROUND

The clinicopathological profiles and outcome of chronic hepatitis B can differ by hepatitis B virus (HBV) genotypes. In Japan, genotype B and C are two major HBV genotypes. The basic core promoter and precore mutations are other known viral factors for disease activity, although the relationship between HBV genotypes and these mutations is not fully understood.

METHODS

The HBV genotypes in 90 patients with chronic hepatitis B were determined using an ELISA. Obtained data were correlated with clinicopathological parameters, basic core promoter, precore and the nucleotide 1858 mutations of the HBV genome.

RESULTS

Among 90 cases, 20 (22.2%) had genotype B and 70 (77.8%) had genotype C HBV. Genotype B patients were older than genotype C patients (44.0 +/- 13.9 vs 34.7 +/- 11.0 P = 0.0022). The HBeAg was more prevalent in genotype C than B patients (P = 0.0008) while anti-HBe was more common in genotype B than C patients (P = 0.0002). Serum aspartate aspartate aminotransferase/alanine aminotransferase levels (B: 220.7 +/- 612.8/257.0 +/- 498.0 IU/L vs C: 111.3 +/- 122.8/201.6 +/- 229.4 IU/L, P = 0.16/0.48) and HBV viral loads in blood (B: 6.1 +/- 3.1 log genome equivalent [LGE]/mL vs C: 6.7 +/- 2.3 LGE/mL, P = 0.42) were equivalent. The seroconversion from HBeAg to anti-HBe occurred significantly earlier in genotype B than C patients (62 +/- 53 months vs 136 +/- 54 months, P = 0.0028) during the mean observation period of 149 +/- 82 months even under various therapeutic modalities. The categories III and IV of the histological activity index in genotype C were higher (III: P < 0.005, IV: P < 0.05, n = 68) than that in B patients whereas category II was higher in genotype B than C patients (P < 0.05). The double mutation (1762T/1764A) in the basic core promoter was more frequently found in genotype C than in B HBV (P = 0.0068), whereas the precore mutation (1896A) was more common in genotype B than C HBV (P = 0.0233). The incidence of 1858C that was complementary to the precore mutation site in the stem-loop structure in, was equally rare in both genotype B and C HBV.

CONCLUSIONS

Genotype B patients were older, had earlier HBeAg seroconversion and exhibited more severe lobular necroinflammation, less portal inflammation and fibrosis than genotype C patients. This genotypic difference is related to the basic core promoter and precore mutations irrespective of 1858C. (c) 2004 Blackwell Publishing Asia Pty Ltd.

Decreased numbers and impaired function of circulating dendritic cell subsets in patients with chronic hepatitis B infection (R2)

BACKGROUND AND AIM

To investigate the frequencies, numbers and function of circulating dendritic cell (DC) subsets in patients with hepatitis B virus (HBV) infection, we assayed the circulating precursor DC subsets (including pDC1 and pDC2) and their ability in patients at various stages of HBV infection in vitro.

METHODS

Circulating pDC1 and pDC2 frequencies in peripheral blood mononuclear cells (PBMC) were analyzed by flow cytometric analysis. Costimulatory molecule expression and allostimulatory mixed lymphocyte reaction (AMLR) of DC1, cultured from PBMC in vitro, were detected in patients with chronic hepatitis B (CHB). On behalf of pDC2, interferon (IFN)-alpha production of PBMC was determined by the ELISA method in HBV-infected patients.

RESULTS

The number of circulating pDC1 decreased only in patients with liver cirrhosis (LC) compared with that in normal controls. However, pDC2 numbers decreased in both CHB and LC patients. DC1 from CHB patients showed lower expression of costimulatory molecules CD80, CD86 and impaired allostimulatory mixed lymphocyte reaction (AMLR) compared with those in normal controls. The ability of PBMC to secrete IFN-alpha also decreased significantly in patients with chronic HBV infection.

CONCLUSIONS

Our results suggest that patients with chronic HBV infection have a significantly lower expression of costimulatory molecules and impaired AMLR of pDC1, as well as decreased number and impaired function of circulating pDC2, which may be partially related to HBV disease progression in these patients.

Evolution of precore/core promoter mutations in hepatitis B carriers with hepatitis B e antigen seroreversion

The evolution of precore stop codon mutation (A1896) and dinucleotide mutation (T1762/A1764) in the basic core promoter (BCP) of hepatitis B virus (HBV) genome during transient seroconversion and seroreversion of hepatitis B e antigen (HBeAg) remains unclarified. Five HBeAg-positive HBV carriers who experienced transient seroconversion followed by seroreversion of HBeAg (Group I, 3.3%) and 3 HBeAg-negative HBV carriers with documented reversion of HBeAg (Group II, 2.5%) in a prospective cohort of 272 patients with chronic hepatitis B were thus identified. The sequential changes at the precore nucleotide 1896 and BCP dinucleotide 1762/1764 were determined by polymerase chain reaction and direct sequencing. At enrollement, precore A1896 and BCP T1762/A1764 were noted in 4 (50%) and 1 (13%) of the eight patients. During a median follow-up period of 58 months (range: 31-76 months), 12 episodes of transient HBeAg seroconversion followed by seroreversion were encountered in Group I patients and 3 episodes of HBeAg seroreversion in Group II patients. Accompanying acute exacerbations were found in two-thirds of patients with either HBeAg seroconversion or seroreversion. Overall, precore nucleotide A1896 remained identical in 73% and 83% of the seroconversion and seroreversion events, respectively. BCP dinucleotide T1762/A1764 remained unchanged in 94% and 92% of the seroconversion and seroreversion events, respectively. At the end of follow-up, only one had both precore and BCP mutations. In conclusion, these data suggested that HBeAg seroreversion might be due to the lack of sustained precore and BCP mutations after HBeAg seroconversion. Although uncommon, HBeAg seroreversion can be associated with hepatitis exacerbation.

Exploring the biological basis of hepatitis B e antigen in hepatitis B virus infection

The function of the hepatitis B e antigen (HBeAg) is largely unknown because it is not required for viral assembly, replication, or infection. In this report we chronicle clinical and experimental studies in an attempt to understand the role of HBeAg in natural infection. These studies largely have focused on clinical-pathologic features of HBeAg-negative variants in acute and chronic HBV infection, mutational analysis in animal models of hepadnavirus infection, and the use of transgenic murine models. The clinical and experimental data suggest that serum HBeAg may serve an immunoregulatory role in natural infection. To the contrary, cytosolic HBeAg serves as a target for the inflammatory immune response. These dual roles of the HBeAg and its ability to activate or tolerize T cells show the complexity of the interactions between the HBeAg and the host during HBV infection.

Hepatitis B virus: prevalence of precore/core promoter mutants in different clinical categories of Indian patients

To determine the association of precore (Pre-C)/basal core promoter (BCP) mutants with clinical outcome of hepatitis B in Western India, 192 hepatitis B virus (HBV) infected individuals were investigated. HBV-DNA PCR positivity among asymptomatic hepatitis B surface antigen (HBsAg) positive carriers (61/100) was lower (P < 0.0001) than chronic hepatitis B (CHB), acute (P = 0.0001), and fulminant hepatitis B patients (P = 0.047). Pre-C status was based on restriction fragment length polymorphism (RFLP, n = 153) and sequencing (n = 118). Prevalence of Pre-C mutants was higher among carriers (23/61) than CHB (10/62, P = 0.0071) or acute (3/22; P = 0.037) patients. Children from carrier and CHB categories showed significantly higher circulation of Pre-C-wild than mutant HBV. Clinical manifestations were independent of BCP mutations (1762/64-T/A). Hepatitis B e antigen (HBeAg) negative CHB patients [62.5% (15/24)] were circulating wild HBV. Higher HBV-DNA levels were associated with chronic hepatitis and HBeAg positivity, whilst Pre-C mutant positives had lower levels. BCP mutations did not affect HBV-DNA levels. Multivariate regression analysis identified HBeAg (OR = 4.3) and Pre-C mutants (OR = 3.1) to be associated with chronic hepatitis and carriers respectively. In a separate sub-set analysis (n = 59), HBV-DNA level was identified as the only variable. In conclusion, chronic or fulminant hepatitis B was not associated with Pre-C or BCP mutants and switching over to Pre-C mutant was beneficial for the infected individual in maintaining disease free status for extended periods.